I think there are two possibilites. One, Bush was given the conclusions and ignored them and continued to say things he knew would make him look like an idiot. Or two, he was basically blindsided by the new estimate. Since the new estimate represents a radical change from the old estimate, I find option two more likely. Both sides try to shade intelligence assessments to advance their policy preferences. It may be wrong, but they do it and it is foolish to ignore that factor. This new estimate seems pretty weak to me, so i think it is fair to view it skeptically. Why, for example, do the Iranians need to be devoting so much effort to uranium enrichment if they are not planning on developing nuclear weapons? Even the new NIE says they could develop weapons within two or three years. That is surely far too rosy a view. With pakistani or russian assistance, they could develop at least a crude device in a matter of months. It's not like they have to have a bomb that can be delivered via ICBM. A truck or ship will do.
I'd give Bush the benefit of the doubt. He wouldnt deliberately claim a country had weapons as a false pretext for war
All this isnt over by a long shot. You all seem to have forgotten another ingredient in this mix, the Israelis. I recall over five or so years ago the Israelis saying to the yanks do something about the Iranians or we will, or something to that effect.